Gastrointestinal Bleeding With Rare Etiology: A Case Report of Primary Aorto-Enteric Fistula: 2000

Primary aorto-enteric fistula (PAEF) is a spontaneous and deadly communication between the abdominal aorta and intestinal tract resulting in an UGI bleed. It is distinguished from secondary, the more common of the two, in the fact that the fistula formation is not preceded by previous aortic surgery or trauma. Atherosclerotic and mycotic-induced abdominal aortic aneurysms (AAA) constitute the majority of PAEF etiologies. Given PAEF's rarity, and oftentimes obscure presentation, knowledge of its existence and a high index of suspicion must be maintained in order to intervene in an otherwise fatal medical phenomenon. We describe the case of a 77-year-old male with HLD and HTN who presented with two-weeks of back pain that progressed to abdominal pain, tarry and bright red stools, and subsequently a syncopal episode one day prior to arrival. On admit, hgb was 10.6. He was hypotensive but stabilized with fluid resuscitation. CT abdomen/pelvis with contrast showed an infrarenal AAA with suspicion for AEF within the transverse duodenum. He was admitted to the ICU for close monitoring. GI was consulted and an urgent EGD was performed which confirmed an AEF in the third duodenum; pulsations and a blood clot were visible at the fistula's opening. He was taken emergently to the cath lab for an endovascular aneurysm repair. Following monitoring in the ICU and then on the general floor, he was ultimately deemed stable for discharge on post-op day six. He followed up with Cardiovascular Surgery for definitive surgery to repair the AEF and aneurysm. With the mortality rate nearing 100% if undiagnosed, PAEF must be considered in any case of unexplained GI bleeding. While the traditional triad includes GI hemorrhage, abdominal pain, and a palpable abdominal mass, vague symptoms such as back pain, melena, and syncope are more typical as seen in this patient. While immediate diagnosis and treatment of PAEF is extremely vital, it is often delayed, and at this time, there is no clear diagnostic method to confirm the disorder. Given its rapid nature, EGD is often first line and an extremely useful diagnostic tool. However, given the disorder's scarcity, it can be easily overlooked, thus, endoscopy is often deemed inconclusive. As seen in this case, CT must also be considered to provide diagnostic evidence in order to heighten suspicion at time of endoscopy. A quick diagnosis is critical and definitive therapy with vascular repair is essential.2000_A Figure 1. CT abdomen/pelvis showing AAA w/ ruptured aorto-enteric fistula.2000_B Figure 2. EGD revealing fistula found in third portion of duodenum.2000_C Figure 3. Repeat CT image showing successful stent graft repair.